Resilient mattresses may generally be classified into two broad categories based on the components which give resiliency to the mattresses, namely coil spring mattresses and foam mattresses.
A coil spring mattresses generally comprises many coil springs extending between upper and lower mattress faces to support the upper and lower faces. In better quality coil spring mattresses, each spring may be compressed a different amount, depending on the load placed on the adjacent mattress face to contour around the load and give relatively even support. It is possible also to use springs having different stiffnesses in different areas of the mattress to better enable the mattress to contour around an irregularly shaped load.
A problem which must be contended with in coil spring mattresses is preventing the coils of adjacent springs from interlocking with one another causing some of the coils to bind rather than restoring themselves to uncompressed height. One method which is commonly used in the industry to prevent such interlocking is to encapsulate each coil in a separate fabric pouch to alleviate the tendency of the coils to interlock. Such encapsulation however adds greatly to the cost of manufacturing a mattress because of the labour and material involved in encapsulating the numerous springs.
Foam mattresses are lightweight and more efficiently manufactured manufacture as compared to coil spring mattresses. Foam mattresses are generally made from an elastomeric material which is initially in a liquid state and is treated in such a way as to evolve gas which causes the material to expand by foaming to form a resilient spongy mass that either sets on its own or requires some subsequent curing step.
The most basic foam mattress is essentially a block of foam which has generally consistent "stiffness" throughout and wouldn't deform in discrete areas in the manner described above for the better quality coil spring mattresses.
The traditional method for texturing the surface of a foam article involves a cutting operation wherein pressure is applied to region of a foam block from opposite sides to compress the foam in the region. The compressed foam is subjected to a transverse cut such as with a band-saw blade. This method divides the foam block into two components with the compressed regions becoming recessed areas when the pressure is removed. This particular method is relatively inefficient both in terms of the amount of machining required and the waste of material. This method also leaves an exposed "cut" surface rather than the "skin" which would ordinarily cover the surface of a foam article as a result of a molding operation. Cutting through the skin reduces the durability of the foam article and yields a surface more prone to frictional binding with another cut surface than would be the case with two uncut surfaces.
Previous attempts have been made to manufacture a foam mattress having individual resilient elements. In one particular mattress, the foam elements are cut into individual blocks and adhered to both sides of a grid-like substrate. Although such a mattress may substantially replicate the comfort of a good quality coil spring mattress, its manufacture is extremely labour intensive. Furthermore in view of the fact that the individual elements are cut and therefore have cut faces, substantial inter-element friction results which affects the ability of the mattress to restore itself to a generally rectangular overall configuration when a load is removed.
It is an object of the present invention to provide a foam mattress having a plurality of discrete spaced apart foam elements to give contourability analogous to a quality coil spring mattress having individual coil springs encapsulated in respective pouches.
It is a further object to the present invention to provide a foam mattress having individual foam elements without excessive friction between the elements thereby allowing the elements to have good restorative capabilities.
A still further object of the present invention is to provide a foam mattress as described above which is more efficient to manufacture as compared to coil spring type mattresses and previous foam element mattresses.
It is yet a still further object of the present invention to provide a foam mattress construction which has zones of different firmnesses selected to correspond to the nature of the load to be supported thereupon.
It is also an object of the present invention to provide a method of making segments which may be incorporated into a foam mattress as described above in which the discrete spaced apart foam elements are molded integrally therewith rather than cut from a foam block.